The present invention is directed to an improvement in the design of an electric door lock actuator, particularly of the type used in an automobile to lock and unlock the latching bolts in the automobile door. More particulary, the present invention is directed to a combination lost motion and spring displacement device for disconnecting the electric door lock actuator from the locking mechanism of the door once the mechanism has moved to a position to secure the latch in the locked or unlocked position.
In most currently utilized electric door lock mechanisms the electric motor armature, gears and portions of the drive train are mechanically coupled to the locked mechanism. The typical system includes a latching bolt to secure the door to the frame of the automobile, an electric switch located on the inside of the door for locking or unlocking the bolt, a manually-displaceable handle inside of the door for unlatching the door, a manually-moveable button, slide or similar device for locking and unlocking a latching bolt in the door, and on the exterior of the door, a handle for latching and unlatching the door and a key opening for receipt of a key for unlocking or locking the latching bolts. The key-receiving mechanism may be designed to either manually unlock the latching bolts or to energize a motor to unlock the latching bolts. At this point in time, most key entry locks utilize the motion imparted by turning the key to unlock the latching bolts.
One of the problems identified with this type of system is that the manual effort required to turn the key to unlock the latching bolt may be significant. If the ambient temperature is low, or there is insufficient lubrication, or a key is particuarly weak, in any of of the above events, the force required to manually unlock the latching bolt may be such that the key is either twisted or broken in the process and entry to the car is denied.
It has been determined that one of the mechanisms acting to create the difficulty in manually unlocking the latching bolts in that when the electric motor, gears, and the remainder of the electric drive train to the door lock actuator are mechanically coupled thereto and in order to manually displace the latching bolt, it is necessary to "back-drive" the gear train and electric motor as the latching bolt is displaced. Hence, additional force on the key is required and additional work is necessary to accomplish the rotation of the motor armature and the displacement of the gear train of the actuator.
The term "back-driven" as used herein is a term used to define the physical movement including rotation of the armature of the actuator motor, and the intermediate gearing between the armature and the door locking mechanism upon manual displacement by turning a key to gain entry to an area.
It has also been identified that under emergency conditions there may be times when it is necessary to unlock a car door from the inside and it is desirable to have little or no parasitic loading due to back-driving. Such emergency conditions include an accident wherein the electrical power source, such as a battery, has become disconnected or the electric motor has been otherwise rendered inoperative. In these circumstances it is likewise beneficial not to have to manually back-drive the motor to accomplish unlocking of the vehicle door.
It is currently known in the art to utilize lost motion devices in door lock actuator units. For instance in U.S. Pat. No. 4,102,213 there is provided a lost motion connection to permit an actuator to cycle even if the door lock lever is being held to preclude movement. This device does not act to isolate manual operation from electric operation to avoid back-driving forces, but instead is directed as a safety feature so as not to destroy the door lock when a person manually holds the lock in a lock position when the unlock button is energized.
U.S. Pat. No. 4,290,634 discloses a series of devices for connecting the manual locking and unlocking button in a car to the motive means. A lost motion relationship is disclosed between items 63 and 62. Spring 64 is utilized to absorb excess energy from a flywheel. In FIGS. 3 and 4 there is disclosed a mechanism for connecting an electric motor to the gear train which is connected to the manual locking button where the gear train is engaged upon sufficient centrifugal force being applied by the motor being operated. Additionally, disclosed in FIGS. 5-8 is a separate type of lost motion device utilized without springs as is the device in FIGS. 9-12. A still further type of device is shown in FIGS. 13-15.
It is also currently known that at least one car manufacturer utilizes an electric door lock actuator which includes an electric motor which drives a rotating mechanism using a spring for latching and unlatching a door. This spring which is a direct part of the drive system is wound when the motor is energized such that when the motor is de-energized, the spring unwinds causing the motor to be rotated backwards thereby allowing for manual operation of the locking mechanism without being required to back-drive the motor.